Thickener component and lubricating grease containing an aluminium complex

ABSTRACT

This invention relates to a thickener component based on an aluminium carboxylate compound and to an aluminium complex grease made therefrom with addition of a base liquid.

[0001] This invention relates to a thickener component based on analuminium carboxylate compound and to an aluminium complex grease madetherefrom with addition of a base liquid.

[0002] Aluminium complex greases have been known. They essentiallycomprise a mineral-oil base liquid and a thickener system containing oneor more aluminium carboxylate compounds. The aluminium carboxylatecompound is obtained by reacting a fatty acid and/or an aromaticcarboxylic acid with an aluminium alcoholate derivative. Theindustrially used aluminium alcoholates comprise aluminiumisopropoxylate and tri-oxy-aluminium-triisopropoxide. In theory, thereaction proceeds as shown hereinbelow:

[0003] When using aluminium isopropoxylate, partial hydrolysis isperformed with water before, during, or after reaction of the acids withaluminium alcoholate to produce the usually required free —OH group onthe aluminium. Aluminium complex greases are distinguished by a highdropping point, good conveyance and water resistance, and low separationof oil.

[0004] It is an object of this invention to provide more effectivealuminium complex greases, in particular more suitable thickenercomponents for manufacturing thickeners for aluminium complex greases.The term ‘more effective’ shall mean that the grease exhibits betterlubricating properties than conventional aluminium complex greases.Furthermore, it is desired that the thickener component employed formaking said aluminium complex greases be storable and marketable assuch, thus enabling the grease manufacturer to produce thethickener-containing grease himself.

[0005] According to this invention, the problem has been resolved byproviding a thickener component comprising

[0006] (A) from 99.99 to 94 weight percent, preferably 99.9 to 97 weightpercent of an aluminium compound which can be prepared by reacting ahydrolysable aluminium compound with one or more aliphaticmonocarboxylic acid(s) or aliphatic derivatives thereof, optionally inthe presence of water and/or a C₁- to C₄₀-alcohol, thereby forming oneor more aluminium compound(s) having at least one aluminium carboxylatebond per aluminium atom and, in addition, one or more aluminium-,hydroxy-, aluminium alcoholate-, or/or aluminium-oxygen-aluminiumbond(s) and

[0007] (B) from 0.01 to 6 weight percent, preferably 0.1 to 3 weightpercent of an ester compound having from 6 to 60 carbon atoms,

[0008] each referring to the total of components (A) and (B).

[0009] The term ‘hydrolysable aluminium compounds’ as used herein refersto aluminium compounds that are capable of forming aluminium-oxygenbonds by the action of proton-donating compounds, such as water ororganic acids. Preferably, such hydrolysable aluminium compounds arealuminium alcoholate- or aluminium-oxo-alcoholate compounds with thealcoholate group preferably being a C₂- to C₄-alcohol, particularlyisopropanolate. The carboxylic acids can be branched or unbranchedaliphatic monocarboxylic acids of the type R¹—COOH, wherein R¹represents a C₁₀- to C₄₀-radical, preferably a C₁₄- to C₂₄-radical, or aC₁₆- to C₂₄-radical.

[0010] Carboxylic acid derivatives as used herein are defined ascompounds which are capable of forming in combination with saidaluminium compounds the aluminium-carboxylate bonds that would likewisebe obtained when using the corresponding acids. Examples thereof includethe anhydrides, acid chlorides, or amides of the aforesaid carboxylicacids.

[0011] Ester compounds as used herein particularly refer to compoundswhich may be formed by reaction of the alcohols/alcoholates present inthe reaction mixture with the carboxylic acids/carboxylate residues.

[0012] The thickener component is prepared by reaction, preferably aboutequimolar reaction, i.e. about 1 mole of monocarboxylic acid per mole ofaluminium atoms in the compound, of a hydrolysable aluminium compoundwith one or more of the abovementioned carboxylic acid(s) or carboxylicacid derivative(s) at a temperature not exceeding 145° C., mostpreferably 135° C., with a temperature profile most preferablyincreasing gradually by at least 20° C. during a period of at least 90minutes being ensured. It is preferred that the hydrolysable aluminiumcompound be placed in the vessel first.

[0013] Moreover, it is preferred that the reaction be carried out in abase liquid and the volatile compound released during the reaction, e.g.alcohol, be withdrawn from the equilibrium.

[0014] The term ‘thickener’ as used herein is defined as a compound ormixture of compounds prepared from the thickener component, whichthickener can be produced by reacting the thickener component witharomatic or cyclic monocarboxylic acids of the type R²—COOH, wherein R²represents a C₆- to C₁₆-radical, or with the derivatives thereof. Said(aromatic or cyclic) carboxylic acid derivatives are defined asdescribed hereinabove.

[0015] The resultant aluminium compound preferably has more than 40 mole% of aliphatic monocarboxylic acid radicals, referring to the amount ofcarboxylate groups (100 mole %=all the carboxylate groups). Theremainder is comprised of aromatic or cyclic monocarboxylic acidradicals.

[0016] As used herein, the term ‘aromatic monocarboxylic acid’ isdefined as a carboxylic acid which has at least one benzene ring orcondensed benzene ring and, in addition, may comprise aliphatichydrocarbn radicals as well. Hence, compounds such as C₆H₅—CH₂—CH₂—COOHor CH₃—CH₂—C₆H₄—COOH are explicitly included herein.

[0017] The thickener as a constituent of the aluminium complex grease isproduced by compounding the thickener component, optionally taken up inadditional base liquid, with the aromatic or cyclic monocarboxylic acid.

[0018] The production process of the invention yields a raw material(thickener component) with a low ester content for making the realthickener that keeps its low ester content even upon storage.

[0019] Besides the thickeners of the invention the aluminium complexgreases of the invention also comprise a base liquid which is ahydrocarbon compound and/or a synthetic oil added to the overallcomposition in quantities of from 30 to 98 weight percent, preferably 60to 95 weight percent.

[0020] The hydrocarbon compound can be a paraffin-base or naphthenicmineral oil, a polyalphaolefin, or a white oil. Further synthetic oilswhich are suitable as base liquid include fatty acid esters based onmono- or multifunctional fatty acids having a chain length of from 8 to24 carbon atoms and mono- or polyhydric alcohols. Additionalconstituents of the aluminium complex greases of the invention may betypical additives. Table 1 presents examples of suitable additives.

[0021] The thickener components of the invention are useful as rawmaterials for producing thickeners included in aluminium complex greasesexhibiting improved lubricating properties. They are preferably employedin high-temperature applications for which high dropping points areespecially desirable, in central lubricators, and/or for lubricatingmachinery used for example for producing or processing foodstuffs.

[0022] The prior art thickeners based on aluminium carboxylate compoundsor the aluminium complex greases made therefrom have significantlyhigher ester concentrations. Surprisingly, compositions with lower esterconcentrations, preferably less than 6% in the thickener component, andimproved lubricating properties have now become accessible by theprocess.

[0023] It is preferred that the thickener components as well contain 20to 80 weight percent, most preferably 30 to 70 weight percent of thebase liquid described hereinabove.

EXAMPLES OF TESTS

[0024] Table 2 shows the rheometric values (Physica UDS 200, oscillatingmeasurement, deformation=0.2%, frequency=0.1 Hz, temperature=20° C.,plate/plate distance=1 mm) of aluminium complex greases of theinvention. Example 4 presents a high ester concentration, whereas theester concentration in Example 5 (comparative example) is too high. Themeasurements were made on a thickener component having an aluminiumcontent of 4.1 weight percent. The solvent in the aluminium-containingthickener component is identical with the base oil. The startingmaterial is aluminium isopropanolate. The aliphatic monocarboxylic acidemployed herein is a technical-grade stearic acid mixture.

[0025] Exemplary Synthesis

[0026] Into a 5-litre agitated vessel equipped with a nitrogen supplyline, a 30-cm column (metalized, packed with Raschig rings), and areflux condenser there are placed 1.466 moles (299.5 g) of DOROX® D 10(aluminium triisopropylate, liquid) and 500.0 g of Sera® 100 mineral oil(approx. 50 wt. % paraffin-base oil). The educts are heated to 97° C.(bottom temperature) while stirring. The stearic acid is heated to75-80° C. to keep the product liquid upon feeding. 1.466 moles (393.5 g)of the liquid stearic acid (acid number=209 mg of KOH/g) and the mixtureof water (1.372 moles=24.7 g) and 2-propanol (123.6 g) are chargedsteadily and simultaneously through separate submerged pipes during aperiod of 2.5 hours.

[0027] The released 2-propanol is removed overhead (head temperaturemax. 85° C.). The bottom temperature is gradually increased to 127° C.during this period. Once the bottom temperature reaches 127° C., thepressure is reduced to 200 hPa during 20 minutes and the remainder ofthe low-boiling 2-propanol is drawn off. During the reaction adistillate comprised of 3.623 moles (217.7 g) of 2-propanol is removedfrom the reaction and the mixture (123.6 g). The product,oxo-aluminium-stearate, is obtained after purification and filtration.The total residence time of the product at 127° C. is 30 minutes (untilend of vacuum phase). Filtration is performed at approx. 120° C. using a60-μm sieve.

[0028] The material parameters of the thickener component have beencompiled in Table 3. TABLE 1 Concentration Range, wt. % Extreme-pressure  2-10 dibenzyldisulfide with chlorinated additives paraffins;sulphurized fatty oils or terpenes Additives for 0.1-5 diisopropyl- ordilauryl enhancing hydrogen phosphite film resistance Rust-inhibiting0.5-5 sodium petroleum sulfonates or additives barium dinonylnaphthalene sulfonate Copper 0.05-1  2-mercaptobenzthiazol deactivatorsViscosity index 0.1-1 polymethacrylates improvers Desludgers 0.001silicone oils Additives for 0.5-2 polymers producing ropiness Antiwear0.1-2 tricresylic phosphate, zinc additives dialkyl dithio-phosphateAdditives for 0.1-2 oil- or other vegetable fatty acids producing waterresistance Deodorants  0.05-0.5 perfumes Anticorrosion 0.5-3nonylphenoxy vinegar, additives ethylenediamine sulfonate, leaddinonylnaphthyl sulfonate, barium sulfonates, lead- and zincnaphthenates Oxidation diphenylamine, phenyl- inhibitorsα-naphthylamine, dioctyldiphenylamine, phenothiazine, polymerictrimethyldihydroquinoline, 2,6-di- tert-butyl-4-methylphenol, leaddiamyl-dithiocarbamate, dilaurylthiodipropionate-1/ citric acid,ascorbic acid

[0029] TABLE 2 Base Liquid Ester Con- Concentra- Thickener Benzoic BaseLiquid Base Liquid centration in tion in Component Acid Con- ViscosityConcentration Thickener Thickener Concentration centration in Modulus ofModulus of at 40° C. in Grease Component Component in Grease GreaseElasticity Viscosity No. Base Liquid mm²/s wt. % wt. % wt. % wt. % wt. %Pa Pa 1 Paraffin-based 100 91.3 1.4 60 7.3 1.4 860 330 mineral oil 2Paraffin-based 100 87.1 1.4 60 10.9 2.0 5,720 1,030 mineral oil 3Paraffin-based 100 82.8 1.4 60 14.5 2.7 35,100 5,400 mineral oil 4Paraffin-based 100 87.1 3.9 60 10.9 2.0 1,100 270 mineral oil 5Paraffin-based 100 87.1 8.7 60 10.9 2.0 800 170 mineral oil 6Naphthene-based 100 87.1 1.2 50 10.9 2.0 5,820 1,000 mineral oil 7Naphthene-based 40 87.1 1.2 50 10.9 2.0 2,680 450 mineral oil 8Polyalpha-olefin 30 91.3 2.4 60 7.3 1.4 290 60 9 Polyalpha-olefin 3087.1 2.4 60 10.9 2.0 2,100 290 10 Polyalpha-olefin 30 82.8 2.4 60 14.52.7 13,300 1,100

[0030] TABLE 3 Method Al content 4.1 % M 635 Turbidity 20 FNU DIN 38404T2 Viscosity (25° C.) 1,500 mPa · s DIN 53015 Viscosity (100° C.) 100mPa · s Rotation (200 s⁻¹) Pour point 16 ° C. DIN ISO 3016 2-Propanolconcentration 3.5 % Density (20° C.) 0.94 g/cm³ DIN 51757 Density (40°C.) 0.93 g/cm³ DIN 51757 Density (50° C.) 0.93 g/cm³ DIN 51757 Flashpoint 190 ° C. DIN 51758 Colour number 10 DIN 6162

1. A thickener component comprising (A) from 99.99 to 94 weight percentof an aluminium compound which can be prepared by reacting ahydrolysable aluminium compound with one or more aliphaticmonocarboxylic acid(s) or derivatives thereof, optionally in thepresence of water and/or a C₁- to C₄₀-alcohol, thereby forming one ormore aluminium compound(s) having at least one aluminium carboxylatebond per aluminium atom and, in addition, one or more aluminium-,hydroxy-, aluminium alcoholate-, or/or aluminium-oxygen-aluminiumbond(s) and (B) from 0.01 to 6 weight percent of an ester compoundhaving from 6 to 60 carbon atoms, each referring to the total ofcomponents (A) and (B).
 2. The thickener component of claim 1,characterised in that the hydrolysable aluminium compound is analuminium alcoholate- or aluminium-oxo-alcoholate compound.
 3. Athickener component according to any one of the preceding claims,characterised in that the aliphatic monocarboxylic acid is a branched orunbranched aliphatic monocarboxylic acid of the type R¹—COOH, wherein R¹is a C₁₀- to C₄₀-radical, preferably a C₁₄- to C₂₄-radical, or aderivative of this monocarboxylic acid.
 4. A thickener componentaccording to any one of the preceding claims, characterised in that atemperature of 145° C., preferably 135° C., is not exceeded during theproduction of the aluminium compound by reacting a hydrolysablealuminium compound with one or more carboxylic acid(s) or carboxylicacid derivative(s).
 5. The thickener component of claim 4, characterisedin that an increasing temperature profile presenting a temperaturedifference of at least 20° C. is maintained at a time interval of atleast 90 minutes during the reaction.
 6. An aluminium complex greasecomprising the composition according to any one of the preceding claimsand, in addition, a base liquid which is a hydrocarbon compound and/or asynthetic oil and which is added to the total composition in quantitiesof from 30 to 98 weight percent, preferably 60 to 95 weight percent. 7.The aluminium complex grease of claim 6, characterised in that the baseliquid has a viscosity of from 20 to 200 mm²/s at 40° C. measured inaccordance with DIN
 51562. 8. The aluminium complex grease of claim 6,characterised in that the base liquid is a mineral oil with a boilingpoint of greater than 250° C.